An Experimental and Theoretical Investigation of Micropiiting in Wind Turbine Gears and Bearings

Kahraman, Ahmet

doi:10.2172/1037344

Cited by 4 publications

(7 citation statements)

References 23 publications

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“…The fatigue lives of the material points are seen to range between 10 6 and 10 14 (no failure) cycles. The crack nucleation sites are observed to be on the surface along the asperity peaks, which agree with the experimental observations [30]. From the distribution of Fig.…”

Section: A Simulation Example: a Ball-on-disk Contactsupporting

confidence: 89%

“…For this purpose, a two-disk test machine is used to perform a number of micro-pitting experiments according to a test matrix constructed using the Fractional Factorial technique, including the potential factors of contact pressure, rolling velocity, slide-to-roll ratio and surface roughness [30]. The direct comparisons between the predictions of the proposed model and these experiments will be presented in a companion paper.…”

Section: Discussionmentioning

confidence: 99%

“…(7a). The accuracy of the boundary element based surface displacement and stress prediction formulation presented above was assessed in a companion study [30] by comparing the BEM solutions with the closed-form solutions for Hertzian contacts. The maximum relative errors were found to be less than 2% for the surface displacements and less than 0.7% for the stress components.…”

Section: Stress Prediction Model For Rough Surface Contactsmentioning

confidence: 99%

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A physics-based model to predict micro-pitting lives of lubricated point contacts

Kahraman

2013

International Journal of Fatigue

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Section: A Simulation Example: a Ball-on-disk Contactsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Stress Prediction Model For Rough Surface Contactsmentioning

confidence: 99%

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A physics-based model to predict micro-pitting lives of lubricated point contacts

Kahraman

2013

International Journal of Fatigue

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“…These ranges of applied normal loads, rolling speeds, and temperature range were chosen to emulate typical operating conditions of a complete wind turbine transmission. The loads and speeds were selected based on a previous study conducted by one of the authors in conjunction with the Department of Energy (DOE) USA, under the Wind & Water Power Program . In this previous study, a complete 750‐kW wind turbine gearbox was molded to investigate the micropitting of wind turbine gearbox components.…”

Section: Experimental Measurement Of Friction Coefficientmentioning

confidence: 56%

“…Here, s = 0.010326 and t = 0.0507; these constant lubricant coefficients were obtained from a large range of regression analysis of PAO ISO VG 320 lubricants. 13 40 In this previous study, a complete 750-kW wind turbine gearbox was molded to investigate the micropitting of wind turbine gearbox components. In terms of the oil temperature specification, the selected oil temperature range used in the test was specified based on experience (where 50 • C represents the temperature at normal ambient temperatures and greater than 80 • C representing extreme oil temperature).…”

Section: Test Specimens and Lubricant Propertiesmentioning

confidence: 99%

An experimental characterization of the friction coefficient of a wind turbine gearbox lubricant

2019

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In this study, a method to predict the contact friction coefficients at the rolling‐sliding contacts of isotropic superfinished and axially ground gear and bearing surfaces in wind turbine gearboxes is proposed. A two‐disc test rig was used to measure friction coefficient values within a slide‐to‐roll ratio range of −0.8 to 0.8, rolling velocities of 2 to 12 m/s, at oil temperatures of 50°C, 70°C, and 100°C and Hertzian contact pressures of 1.2, 1.6, and 2.0 GPa. A polyalphaolefin (PAO) International Standards Organization (ISO) viscosity grade (VG) 320 was the lubricant. Data from 90 individual friction coefficient tests were combined to develop two closed‐form friction coefficient formulae. A multivariable linear regression analysis was used to derive the regressed formulae. Using the developed regressed formulae, the predicted friction values follow the trend of measured values at all of the operating conditions. The results show that the regressed formulae are close to experimental friction coefficient values. The friction coefficient predictions confirm that the regressed formulae are capable of simulating contact friction values for the lubricated contact conditions considered.

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Dynamic modeling of gears: An innovative hybrid FEM–analytical approach

Concli¹,

Gorla²

2021

Int. J. CMEM

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Gearboxes are widely used in several applications ranging from the automotive to the industrial and robotic sectors. A planetary gearbox is a special kinematic gear arrangement that, taking advantage of a planet carrier, ensures high reduction ratios together with a very small design. Therefore, they are widely employed for transmissions which require a high power density. There are several fields of applications including, but not limited to, mechatronic, automation and wind power generation. To improve the design of new solutions, for performing monitoring activities on actual gearboxes and for the definition of maintenance schedules, the availability of physical models able to accurately describe the behavior of the system, both in healthy and damaged conditions, would represent a great support. Experimental and numerical studies of the behavior of gearboxes are already available in the literature. Nevertheless, while the experimental approaches are valid only for the specific configuration tested, the numerical techniques show limitations related to the computational effort required. This paper presents an innovative approach for the characterization of the behavior of two different geared transmissions. It is based on a hybrid approach that combines finite elements (FE) with analytical formulations. In detail, the solver computes separately the macro deformation of the bodies (numerical solution based on a coarse grid) and the contacts (solved analytically avoiding the need of mesh refinements). The computational effort is reduced significantly without affecting the accuracy of the results significantly. This approach was used to investigate and understand the vibro-dynamical behavior of a back-to-back test rig (typically used for the characterization of the surface fatigue strength of gears) and of an industrial planetary gearbox. The results obtained for the healthy -not damaged -gearboxes were compared with experimental measurements for both configurations in order to validate the hybrid approach. Once the models were validated, the same methodology was eventually used to study the effects of typical gear failures and in specifically surface fatigue (pitting), on the vibrational response. The capability to reproduce the effect of damages with the model of a gearbox represents the first indispensable step of a Structural Health Monitoring strategy. State-of-art and challenges are analyzed and discussed in the paper.

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An Experimental and Theoretical Investigation of Micropiiting in Wind Turbine Gears and Bearings

Cited by 4 publications

References 23 publications

A physics-based model to predict micro-pitting lives of lubricated point contacts

A physics-based model to predict micro-pitting lives of lubricated point contacts

An experimental characterization of the friction coefficient of a wind turbine gearbox lubricant

Dynamic modeling of gears: An innovative hybrid FEM–analytical approach

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